This application claims the priority of German application 103 28 452.4, filed Jun. 25, 2003,
This invention relates to a method for creating a hole on the outer circumference of a hollow profile which is circumferentially closed and under an internal high pressure, and to a device for carrying out such a method.
A method of this general type and a device of this general type are known from German publication DE 197 52 171 A1. In the method described in this publication, a tubular hollow profile is placed into an internal high-pressure forming mold, which is subsequently closed. An internal high pressure is then produced inside the hollow profile and makes the hollow profile expand until it comes to bear with its walls against the impression of the internal high-pressure forming mold. A bore in which a hole punch is guided branches off from the impression. After the expansion of the hollow profile, the end face of the hole punch facing the impression butts against the outer side of said hollow profile. To create a hole on the outer circumference of the hollow profile, the hole punch is driven by a driving element on the side facing away from the impression. This takes place by the hole punch penetrating into the hollow profile and thereby cutting out a punched slug. Since the lateral sealing of the hole punch in the forming mold and the internal high pressure are maintained, the punched slug remains attached to the end face of the hole punch. The hole punch together with the punched slug is thereafter retracted into the guiding bore of the hole punch. As a result, a hole-shaped opening is formed in the wall of the hollow profile. Generally, the hole punch is driven by a hydraulic cylinder as the driving element, which is arranged such that it is colinear in relation to the center axis of the guiding bore of the hole punch on the internal high-pressure forming mold. Such hydraulic cylinders have large volumes and require relatively large installation spaces. Consequently, the use of such hydraulic cylinders in connection with confined installation spaces and regions of the hollow profile within the internal high-pressure forming mold to which access is difficult is virtually impossible. As a result, the versatility of hole creation in the internal high-pressure forming mold is restricted considerably. Disadvantageously, therefore, the hollow profile cannot be punched as desired, and it is inconveniently necessary to forgo the internal high-pressure forming mold in favor of other conventional molds to make it possible for the holes to be produced. On the other hand, when punching holes with conventional molds, without the presence of a fluidic high pressure as a supporting pressure, the hollow profile contour loses its dimensional stability due to indentations and the like.
One object of this invention is the object of developing a method of the type mentioned to the extent that it is made possible for holes to be punched at virtually any desired location in hollow profiles in the internal high-pressure forming mold in a simple way.
This object is achieved according to an inventive method by way of a punch which is integrated in an internal high-pressure forming mold such that it can be guided, which, when it leaves its position of abutment, creates a punched slug there alongside the hole, and which is acted on by a driving element. The driving element has a body axis which lies approximately at 90° in relation to a hole punch axis, and is driven in at least one of a rotary manner and a translatory manner in the axial direction, against a location of the hole to be created. Hole-punching results from moving the punch in a guiding bore of the forming mold by way of the internal high pressure acting together with the driving element. The object mentioned is also achieved according to an inventive device by way of a punch, which is guided in an internal high-pressure forming mold and which, before hole-punching, butts against the location of the hole to be created, and a driving element for driving the punch. A body axis of the driving element is arranged approximately at 90° in relation to the hole punch axis, and the driving element is driven in at least one of a rotary manner and a translatory manner in the axial direction. The driving element acts with a driving contour on a punch head arranged on a side of the punch facing away from a mold impression acting together with an internal high pressure driving the punch outward.
On account of the special arrangement of the driving element axis, which extends approximately at 90° in relation to the hole punch axis, in combination with drive contours which are arranged on the driving element and act on the punch head of the hole punch, the movement of the drive of the driving element which causes the driving of the hole punch is deflected, whereby the two drives lead to directions of movement of the driving element and the hole punch that are different from each other. This allows the drive of the hole punch to be led out from the forming mold in a space-saving way, making it possible to dispense with the high-volume colinear arrangement of the drive for the hole punch. The drive for the driving element, which may for example also be a servo motor, can then be arranged on the forming mold in regions which are easily accessible and where no complications of a structural or design-related nature with already existing mold parts of the forming mold occur. The hole-punching operation is consequently virtually independent of the installed location of the drive for the hole punch or of the installed location of the driving element, so that hole-punching is possible at virtually any desired location of the hollow profile. Furthermore, the invention even makes it possible, in a way which saves installation space, to accommodate the driving element within the forming mold; suitable bores or clearances have to be provided for this purpose. Furthermore, it is no longer necessary to carry out an adaptation of the control of the hydraulics and the electrics of the hydraulic cylinder, as previously required for setting the hole-punching operation, which in the past involved considerable expenditure in terms of apparatus. This setting is now accomplished in a simple way by a suitable design of the drive contours of the driving element.
Expedient refinements of the invention will be apparent from the dependent claims; otherwise, the invention is explained in more detail below on the basis of several exemplary embodiments represented in the drawings.